const_expression_value
long long const_expression_value(struct expression *);
alignment = const_expression_value(expr);
alignment = const_expression_value(expr);
width = const_expression_value(expr);
if (cond && !const_expression_value(cond) && cond->type == EXPR_VALUE)
idx_from = const_expression_value(from);
idx_to = const_expression_value(to);